1. Field of the Invention
The present invention relates to resistive termination of a transmission line. In particular, the present invention relates to providing resistive termination and gain in a low-noise amplifier.
2. Discussion of the Related Art
In some applications, a single-ended input signal is required to be matched to a 50 ohm input impedance and preamplified. FIG. 1 shows a circuit 100 in the prior art for terminating an input signal. In FIG. 1, the input signal and its associated input impedance R.sub.s are modeled by a voltage source 101 (with a variable voltage V) and by resistor 102. A fixed gain amplifier 103 and a resistor 104 provide both a gain and matching of the input impedance. Amplifier 103 is selected to have a fixed gain of -m over the operating frequency range and resistor 104 is selected to have a resistance (m+1)R.sub.s, so that the negative feedback signal provided by resistor 104 clamps the input voltage at amplifier 103 at voltage V/2 (i.e., the input impedance is matched).
To provide a substantial gain, however, prior art circuit 100 requires a substantial current source in amplifier 103 to ensure linearity within the dynamic range of the input signal.